From 3d0c4f0240820fbcc82ef5aef605d8731045c25a Mon Sep 17 00:00:00 2001
From: tuftedocelot <tuftedocelot@fastmail.fm>
Date: Wed, 20 May 2020 19:56:07 -0500
Subject: [PATCH] Add previously existing work

---
 pyModeS/decoder/acas.py | 50 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 50 insertions(+)

diff --git a/pyModeS/decoder/acas.py b/pyModeS/decoder/acas.py
index 139d1ff..24919fd 100644
--- a/pyModeS/decoder/acas.py
+++ b/pyModeS/decoder/acas.py
@@ -3,10 +3,60 @@ Decoding Air-Air Surveillance (ACAS) DF=0/16
 
 [To be implemented]
 """
+from __future__ import absolute_import, print_function, division
 
 from pyModeS import common
 
 
+def threat_type(msg):
+    """
+    Determine the threat type indicator
+
+    ===== =======
+    Value Meaning
+    ===== =======
+    0     No identity data in TID
+    1     TID has Mode S address (ICAO)
+    2     TID has altitude, range, and bearing
+    3     Not assigned
+    :param msg:
+    :return: indicator of threat type
+    """
+    mb = common.hex2bin(msg)[32:]
+    tti = common.bin2int(mb[28:30])
+    return tti
+
+
+def threat_identity(msg):    
+    mb = common.hex2bin(msg)[32:]
+    tti = threat_type(msg)
+    
+    # The ICAO of the threat is announced
+    if tti == 1:
+        return common.icao(mb[30:55])
+    else:
+        raise RuntimeError("%s: Missing threat identity (ICAO)")
+    
+    
+def threat_location(msg):
+    """
+    Get the altitude, range, and bearing of the threat
+    Altitude is the Mode C altitude
+    :param msg:
+    :return: tuple of the Mode C altitude, range, and bearing
+    """
+    mb = common.hex2bin(msg)[32:]
+    tti = threat_type(msg)
+    
+    # Altitude, range, and bearing of threat
+    if tti == 2:
+        grey = mb[31] + mb[32] + mb[33] + mb[34] + mb[35] + mb[36] + mb[38] + mb[38] + mb[39] + mb[40] + mb[41] + mb[42] + mb[43]
+        mode_c_alt = common.gray2alt(grey)
+        _range = common.bin2int(mb[44:51])
+        bearing = common.bin2int(mb[51:57])
+        return mode_c_alt, _range, bearing
+
+
 def has_multiple_threats(msg):
     """
     Indicate if the ACAS is processing zero, one, or more than one threat